The present invention relates to a check valve for arranging between a first pressure chamber, in which a first pressure of a fluid prevails, and a second pressure chamber, in which a second pressure prevails, comprising a valve housing on which a valve seat is formed, and comprising a blocking element which is designed in a blocking position to close a valve opening in the region of the valve seat, in order to block a connection between the first and the second valve chambers when the second pressure is greater than the first pressure and is designed in an open position to release the valve opening in order to release the connection between the first and the second valve chambers when the first pressure is greater than the second pressure, the fluid being able to flow in the open position in a flow direction from the first pressure chamber into the second pressure chamber.
The present invention further relates to a fluid pump comprising a pump housing and a piston displaceably mounted therein which forms with the pump housing a pressure chamber, a suction connector of the pump being connected to the pressure chamber via a first check valve and the pressure chamber being connected to a pressure connector of the pump via a second check valve.
Such a check valve is generally known. A check valve is generally used for determining the direction of the flow of a fluid and is a directional control valve which automatically blocks the passage of fluid in one of the two flow directions.
So-called ball check valves are known, in particular, in which the blocking element is formed by a ball, which is pressed by a spring into the valve seat.
In an alternative embodiment, the valve seat is arranged perpendicular to the flow direction and closed by a flap. The flap may in this case be suspended on an upper region, in particular, so that it automatically reaches the blocking position due to its own weight.
A drawback with such check valves is, on the one hand, the large number of components. On the other hand, in particular with a check valve comprising a flap, the fluid flow in the open position is interrupted by the flap which is initially aligned approximately perpendicular to the flow direction. This leads to a relatively low degree of efficiency. Moreover, the frequencies which may be achieved when rapidly changing from the blocking position into the open position and vice versa are relatively low.
Piston pumps are pumps for conveying fluids, in a first stroke the fluid to be conveyed being suctioned in through an inlet valve by the piston. Subsequently, in a second stroke the fluid is ejected through the outlet valve. Such a pump may also be denoted as a displacement pump.
Due to the high pressures which are achievable, it is not excluded that fluid escapes between the pump and the pump housing. This may be undesirable in closed circuits. Moreover, it may also be undesirable if the fluid has the tendency to crystallize or to form clumps when at a standstill. This applies, for example, when using the fluid pump for pumping urea. Such pumps are used in urea injection systems, as are used in systems for cleaning the exhaust gas of vehicles operated by diesel engines (so-called DNOX systems).